- Change in Each Component of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2019		Sep. 30, 2018		Sep. 30, 2019	Sep. 30, 2018
Change in accumulated other comprehensive loss balances:
Unrealized net gains (losses) on hedges arising during the period, before tax	$ 41
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	11
Unrealized net gains (losses) on hedges arising during the period, net of tax	30				$ 81	$ (72)
Reclassification adjustment for net (gains) losses on hedges included in interest income for loans and interest expense on long-term debt, net of tax	20		$ 8		49	14
Net change, before tax	68		11		177	(79)
Net change, tax	(18)		(3)		(47)	21
Net change, net of tax	50		8		130	(58)
Unrealized holding gains (losses) arising during the period on securities available for sale, net of tax	53		(51)		358	(289)
Reclassification adjustment for net (gains) losses on securities available for sale included in securities gains, net, net of tax	(8)		(1)		(25)	(3)
Amortization of net unrealized (gains) losses on held to maturity securities, net of tax	8		6		18	15
Net change, before tax	72		(63)		476	(376)
Net change, tax	(19)		17		(125)	99
Net change, net of tax	53		(46)		351	(277)
Foreign currency translation adjustment, net of tax						(2)
Amortization of prior service credit, net of tax	(7)	[1]	(8)	[1]	(22)	(23)
Recognized net actuarial (gain) loss, net of tax	14	[1]	18	[1]	41	53
Net change, before tax	8		14		25	41
Net change, tax	(1)		(4)		(6)	(11)
Net change, net of tax	7		10		19	30
Other, before tax	0				1	(1)
Other, tax	0				0	0
Other, net of tax	0		0		1	(1)
Other Comprehensive Income (Loss), before Tax	148		(38)		679	(418)
Other Comprehensive Income (Loss), Tax	(38)		10		(178)	110
Other Comprehensive Income (Loss), Net of Tax	110		(28)		501	(308)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	(27)		(11)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	(7)		(3)
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, before Tax	71		(70)
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax	18		(19)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax	11		1
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax	3		0
Other Comprehensive Income Amortization of Net Unrealized Losses on Held To Maturity Securities Before Tax	(12)		(8)
Other Comprehensive Income Amortization of Net Unrealized Losses on Held To Maturity Securities Tax	(4)		(2)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax						(3)
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax						1
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	(10)		(10)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, Tax	(3)		(2)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	(18)		(24)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, Tax	$ (4)		$ (6)
Net Unrealized Gains (Losses) on Cash Flow Hedges
Change in accumulated other comprehensive loss balances:
Other Comprehensive Income (Loss), before Reclassifications, before Tax					110	(98)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax					67	19
Reclassification from AOCI, Current Period, Tax					(18)	(5)
Other Comprehensive Income (Loss) before Reclassifications, Tax					(29)	26
Accumulated Net Investment Gain (Loss) Arising During the Period, Attributable to Parent [Member]
Change in accumulated other comprehensive loss balances:
Other Comprehensive Income (Loss), before Reclassifications, before Tax					485	(392)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax					(34)	(4)
Reclassification from AOCI, Current Period, Tax					9	1
Other Comprehensive Income (Loss) before Reclassifications, Tax					(127)	103
Accumulated Net Investment Gain (Loss), Held to Maturity Securities, Attributable to Parent [Member]
Change in accumulated other comprehensive loss balances:
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax					25	20
Reclassification from AOCI, Current Period, Tax					(7)	(5)
Foreign Currency Translation Adjustment
Change in accumulated other comprehensive loss balances:
Other Comprehensive Income (Loss), Net of Tax					0
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Change in accumulated other comprehensive loss balances:
Other Comprehensive Income (Loss), before Reclassifications, before Tax					(30)	(31)
Other Comprehensive Income (Loss) before Reclassifications, Tax					8	8
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Change in accumulated other comprehensive loss balances:
Other Comprehensive Income (Loss), before Reclassifications, before Tax					55	72
Other Comprehensive Income (Loss) before Reclassifications, Tax					$ (14)	$ (19)

[1] (Dollars in millions) BeforeTaxAmount TaxEffect Net ofTaxFor the Three Months Ended September 30, 2018 Cash flow hedge activities: Reclassification adjustment for net (gains) losses on hedges included in interest income for loans and interest expense on long-term debt 11 (3) 8Net change 11 (3) 8Securities: Unrealized holding gains (losses) arising during the period on securities available for sale (70) 19 (51)Reclassification adjustment for net (gains) losses on securities available for sale included in securities gains, net (1) — (1)Amortization of net unrealized (gains) losses on held to maturity securities 8 (2) 6Net change (63) 17 (46)Pension and other benefits: Amortization of prior service credit(1) (10) 2 (8) Recognized net actuarial (gain) loss(1) 24 (6) 18Net change 14 (4) 10Net change in AOCI $(38) $10 $(28)